The present invention relates to an oil based red ink for a ball point pen and a ball point pen itself. More specifically, it relates to an oil based red ink for a ball point pen, the color of which can be observed from the outside when it is filled into a transparent or translucent ink reservoir and the visual color of which is close to that of the drawn lines, and a ball point pen using the same.
In conventional oil base red inks for a ball point pen, the visual color in the state where the ink is filled into an ink reservoir is different to a large extent from a color of the drawn lines. The visual color thereof is almost close to a black color in many cases, and it has been impossible to identify what color ink is filled into an ink reservoir from the outside of the ink reservoir. Accordingly, in such case, the ink reservoir has been colored to a red color to thereby make it possible to find that a red ink is filled thereinto.
Further, even in the case where it can be found from the appearance of an ink reservoir that a red ink is filled thereinto, there has been such a big difference in a color that while the visual color is dark red, drawn lines obtained in writing have a vivid red color.
The present invention has been made in light of the problems described above, and an object thereof is to provide an oil based red ink for a ball point pen, the visual color of which can be identified through an uncolored and transparent or translucent ink reservoir and a barrel of a ball point pen which transmits light and the color of which is close to a color of the drawn lines obtained in writing, and a ball point pen using the same.
Intensive researches repeated by-the present inventors in order to solve the problems described above have resulted in finding that use of an ink in which a spectral reflectance (%) determined in the state where the ink is filled into an ink reservoir is 20% or more at least in a longer wavelength area than 620 nm and in which a spectral reflectance-rapid increase area which is the area where a difference between a spectral reflectance in the area and an average spectral reflectance in 400 to 560 nm is plus 4% or more is present between 580 to 600 nm solves the conventional problems described above and makes it possible to identify a color of the ink by visual observation through the transparent ink reservoir and the transparent barrel of the ball point pen. Thus, the present invention has hen completed.
That is, the oil based red ink for a ball point pen of the present invention comprises at least one organic solvent selected from the group consisting of alcohols and glycol ethers, a resin and a colorant, wherein a spectral reflectance (%) determined in a state where the above ink for a ball point pen is filled into an ink reservoir is 20% or more at least in a longer wavelength area than 620 nm; and a spectral reflectance-rapid increase area which is the area where a difference between a spectral reflectance in the area and an average spectral reflectance in 400 to 560 nm is plus 4% or more is present between 580 to 600 nm.
The ball point pen of the present invention is characterized by charging an ink reservoir with the oil based red ink for a ball point pen described above.
xe2x80x9cThe spectral reflectance (%) is 20% or more at least in a longer wavelength area than 620 nmxe2x80x9d in the present invention means that a measured value of the spectral reflectance determined in the state where the ink for a ball point pen of the present invention is filled into an ink reservoir is 20% or more at least in a longer wavelength area than 620 nm. Accordingly, it also includes an ink having a spectral reflectance of 20% or more in a shorter wavelength area than 620 nm (for example, 600 nm), which is determined in the state where the ink for a ball point pen of the present invention is filled into an ink reservoir.
Further, xe2x80x9ca spectral reflectance-rapid increase area which is the area where a difference between a spectral reflectance in the area and-an average spectral reflectance in 400 to 560 nm is plus 4% or more is present between 580 to 600 nmxe2x80x9d in the present invention means that the ink for a ball point pen of the present invention has a spectral reflectance-rapid increase area in 580 to 600 nm in the state where the above ink is filled into an ink reservoir and that-a value obtained by deducting an average value of a measured value of the spectral reflectance in 400 to 560 nm from a measured value of the spectral reflectance at any wavelength falling in a range of 580 to 600 nm corresponds to plus 4% or more.